The invention relates generally to an image forming device, and more particularly, to the sensing of toner levels in a toner container.
During the image forming process, toner is transferred from a toner supply container to toner carrying members and to print or copy media. Inefficiencies in the transfer process cause residual toner to remain on the toner carrying members or other transport members, such as transport belts, intermediate transfer belts/drums, and photoconductive members. Residual toner may also be created during registration, color calibration, paper jams, and over-print situations. This residual toner should be cleaned before it affects the quality of subsequent images. A blade or other cleaning device commonly removes the residual or waste toner and the removed toner is stored in a waste toner container.
Over time, toner levels in the toner supply container fall while levels in the waste toner container rise. Clearly, it is desirable to know the toner level in these containers. If the toner supply container nears an empty condition, print quality may suffer. Meanwhile, if a waste toner container overfills, the toner will spill into other regions of the image forming device, thus creating a mess and potentially causing print defects or other malfunctions. Estimates of toner use and accumulation based on print or time counts may not be accurate due to variability in factors such as environment, developer age, patch sensing cycles, transfer parameters, and the duration of operation without paper in the transfer path.
Accordingly, some type of level-sensing may be appropriate in the toner containers. Some known types of toner level sensors include electrical sensors that measure the motive force required to drive an agitator within the container, optical devices using mirrors and toner dust wipers in a container, and other opto-electro-mechanical devices such as a flag that moves with the toner level to actuate a sensor that triggers only when the volume reaches a predetermined level. Unfortunately, there are drawbacks to these known sensors that make these solutions less than ideal. For instance, toner agitation may create unwanted toner dust and the added complication of moving hardware. Furthermore, the addition of moving parts increases component complexity and opportunities for errors. Therefore, existing solutions may not provide an optimal means for detecting toner levels in a toner container within an image forming device.